1. Technical Field
The present invention relates in general to improved processing of disk drive components and, in particular, to an improved system, method, and apparatus for monitoring a condition of a burnish head during a magnetic media cleaning and/or burnish process.
2. Description of the Related Art
Generally, a data access and storage system consists of one or more storage devices that store data on magnetic or optical storage media. For example, a magnetic storage device is known as a direct access storage device (DASD) or a hard disk drive (HDD) and includes one or more disks and a disk controller to manage local operations concerning the disks. The hard disks themselves are usually made of aluminum alloy or a mixture of glass and ceramic, and are covered with a magnetic coating. Typically, two or three disks are stacked vertically on a common spindle that is turned by a disk drive motor at several thousand revolutions per minute (rpm).
A typical HDD also includes an actuator assembly. The actuator moves magnetic read/write heads to the desired location on the rotating disk so as to write information to or read data from that location. Within most HDDs, the magnetic read/write head is mounted on a slider. A slider generally serves to mechanically support the head and any electrical connections between the head and the rest of the disk drive system. The slider is aerodynamically shaped to glide over moving air in order to maintain a uniform distance from the surface of the rotating disk, thereby preventing the head from undesirably contacting the disk.
Typically, a slider is formed with an aerodynamic pattern of protrusions (air bearing design) on its air bearing surface (ABS) that enables the slider to fly at a constant height close to the disk during operation of the disk drive. A slider is associated with each side of each platter and flies just over the platter's surface. Each slider is mounted on a suspension to form a head gimbal assembly (HGA). The HGA is then attached to a semi-rigid actuator arm that supports the entire head flying unit. Several semi-rigid arms may be combined to form a single movable unit having either a linear bearing or a rotary pivotal bearing system.
To successfully achieve file performance, the heads must fly steadily at a given fly height over the disk with minimal variations. Since the variations in fly height are dependent on the various sensitivities of the fly height to the process parameters as well as the variability of the parameters, tight process control is mandatory to minimize such variations. Common dominant process parameters affecting fly height include gram load, pivot location, crown and etch depths.
The presence of asperities on the surfaces of the disks is a major factor that can have a deleterious effect on the performance of disk drives. Asperities can contact the magnetic head as it flies at its normal height in a disk drive. For this reason, a glide test is performed on finished disks to detect asperities that might contact the magnetic head during operation. In the test, a special glide head containing a piezoelectric transducer (PZT) is flown over a disk at an altitude or height that is below the normal drive fly height. Glide head contact with an asperity creates a PZT voltage response that generally scales with increasing size of the asperity. If the voltage response exceeds a predetermined level, the disk is rejected.
One way to reduce such disk defects is to burnish the disks. A thin film disk head burnish process removes the disk surface debris and asperities that are introduced by pre- and post-sputter processes. As stated above, such debris and asperities can reduce disk glide yield and cause other significant disk drive performance problems. The burnish process is utilized on thin film media to remove asperities and loose particles before it can go for glide and magnetic certification tests. Burnishing is typically performed in two steps: a tape burnish process followed by a head burnish. Presently, the burnish heads themselves are not monitored or evaluated while in operation. In particular, there have been no attempts to maintain the status of burnish heads at the media glide and magnetic certification testers. Thus, it would be desirable to be able to better understand and evaluate the condition of burnish heads during operation.